During sheet metal forming, the surface finish changes as the sheet slides bends, and stretches against the tools. Specially engineered surface finishes have been developed by automakers to improve forming consistency and painting quality. This study assessed the evolution of surface parameters
on aluminum sheet surface finishes during manufacturing processes. The scope of this work is experimental. Two surface finish conditions were studied, mill finish (MF) and electro discharge texture (EDT). The 3D Surface roughness conditions were determined for these materials in both the longitudinal and the transverse rolling directions of the sheet. The sheets were tested using several tests (i) three pin Draw Bead Simulator (DBS) tests, tests run under fix and roller conditions, (ii) pure bending moment tests, (iii) and tensile tests. A 3-D Wyko profilometer was used to take the surface roughness measurements.
The changes in surface roughness due to bending effects tension effects, and contact effects are investigated for both material types and rolling directions. The results indicate that the creation of new surface features during tensile straining under both bending and tension are more significant in influencing surface textures in MF sheet than in EDT sheet. During the initial
change in curvature for DBS and pure bending moment tests from flat to concave the MF samples experienced an average increase in roughness 390% greater than EDT. This trend is observed in similar strain directions undertaken during the cycles investigated. Conversely, the effects of contact than in MF at the middle pin. At that location, the transition from an uncontacted convex surface to a concave surface under DBS contact pressure results in a surface roughness 10% less than the starting value for EDT
samples, whereas MF returns to approximately the original value. This study showed changing trends on the surface roughness of sheet metal under bending and tension. It also shows a methodology to assess those roughness changes. The understanding of the contact effects on surface roughness for sheet textures may provide insight for further texture
optimization and to the understanding of friction itself.